1. Field of the Invention
The present invention relates to a lockup device. More specifically, the present invention relates to a lockup device used in a torque converter or other fluid-type torque transmission device.
2. Background Information
A conventional torque converter has a torus part having three types of bladed wheels, typically an impeller, a turbine, and a stator. The torque converter transmits torque by means of an operating fluid contained therein. The impeller is fixed to a front cover, which is coupled to an input-side rotating body. The turbine is driven by the working fluid flowing from the impeller and is coupled to an output member.
Inside some conventional torque converters, a lockup device is arranged in the space between the turbine and the front cover. The lockup device serves to transmit torque directly from the front cover to the output member. This kind of lockup device is generally equipped with a piston that is coupled to a turbine shell or other output member. A friction member is fixed to a lateral surface of the piston. When the friction member presses against the friction surface of the front cover, the torque from the front cover is mechanically transmitted to the output member.
In this example of the prior art, the lockup device has only one friction surface and sometimes, when the engine torque is large, the torque transmission capacity of the lock up device is insufficient. In response to this problem, lockup devices have been made that use a multiple plate clutch to increase the torque transmission capacity. This kind of lockup device is provided with, for example, a damper mechanism, a friction plate, and a piston. The friction plate engages with an outside circumferential part of the damper mechanism in such a manner that it can move in the axial direction. Further, the piston is provided to press the friction plate against a friction surface of the front cover or a plate fixed to the front cover. The damper mechanism has, for example, a plurality of coil springs, a pair of drive plates for supporting the coil springs in the axial and rotational directions, and a driven plate disposed between the drive plates and coupled to the turbine. The outer circumferential parts of the two drive plates are fixed together by, for example, a plurality of stop pins. Further, an engaging ring member is fixed on the outside circumferential surface of the drive plates. The friction plate engages with the engaging member in such a manner that it cannot rotate but can move in the axial direction relative thereto.
The radial dimension of the lockup device just described is relatively large because the stop pins and engaging ring are arranged on an outside circumferential part of the damper mechanism.
In view of the above, there exists a need for a lockup device for a fluid-type torque transmission device that overcomes the above-mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the present invention is to save space in a lockup device that has a friction plate arranged on the outside circumferential part of the damper mechanism for securing torque transmission capacity.
A lockup device in accordance with a first aspect of a preferred embodiment of the present invention is used in a fluid-type torque transmission device. The fluid-type torque transmission device has a front cover, an impeller, and a turbine. The impeller is fixed to the front cover so as to form a fluid chamber. Further, the turbine faces the impeller inside the fluid chamber. The lockup device is disposed inside the fluid chamber in the space between the front cover and the turbine. Further, the lockup device is provided with a clutch-purpose friction plate, a pair of drive members, a driven member, and an elastic member. The clutch-purpose friction plate can couple with the front cover so as to rotate integrally. The pair of drive members is a pair of disk-shaped members, first and second disk-shaped members, disposed so as to be spaced axially apart from each other. The drive members have a cylindrical part that extends from the outside circumferential edge of the first disk-shaped member toward the second disk-shaped member. The cylindrical part engages with the inside circumferential edge of the friction plate such that the friction plate cannot rotate but can move in the axial direction relative thereto. The driven member is fixed to the turbine. The elastic member is compressed by the pair of drive members and the driven member when the drive members and driven member rotate relative to each other.
In this lockup device, the friction plate engages with the cylindrical part of a drive member and the pair of drive members is not provided with a member for supporting the friction plate. Consequently, in the case of a lockup device having a friction plate provided on the outside of a damper mechanism, the radial dimension of the entire device can be made smaller relative to conventional devices.
A lockup device for a fluid-type torque transmission device in accordance with a second aspect of the present invention is the lockup device of the first aspect, having a first and a second set of protrusions and recessions. The first set of protrusions and recessions is aligned in the circumferential direction and is formed on the outside circumferential surface of the cylindrical part. The second set of protrusions and recessions is aligned in the circumferential direction and engages with the outside circumferential surface of the cylindrical part. The second set of protrusions and recessions is formed on the inside circumferential edge of the friction plate.
A lockup device for a fluid-type torque transmission device in accordance with a third aspect of the present invention is the lockup device of the first or second aspect, wherein a fixing part is formed on a tip end of the cylindrical part. The fixing part is bent radially inward and fixed to the second disk-shaped member.
In this lockup device the conventional stop pins can be omitted because a fixing part is provided on the tip end of the cylindrical part. Consequently, the radial dimension of the entire lockup device can be made even smaller.
A lockup device for a fluid-type torque transmission device in accordance with a fourth aspect of the present invention is the lockup device of the first or second aspect, wherein a fixing part is formed on the outside circumferential edge of the second disk-shaped member. The fixing part extends in the axial direction inside the cylindrical part and is fixed to the first disk-shaped member.
In this lockup device the conventional stop pins can be omitted because a fixing part is provided on the outside circumferential edge of the second disk member. Consequently, the radial dimension of the entire lockup device can be made even smaller.
These and other objects, features, aspects, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.